Multi-tube reactors of this type are known and have been described in open German Application DE-OS No. 28 46 693 and the corresponding U.S. Pat. No. 4,263,141.
The tubes of the known tubular reactors contain a bulk material consisting of a granular catalyst.
The tubes are formed in concentric circular arrays, and the ratio of the diameters of the outermost and innermost circular arrays varies between 10:1 and 20:1, depending on the design of the reactor structure.
As the liquid used to supply or extract heat flows along the tubes, the liquid must flow past numerous circular arrays of tubes so that a high pressure drop results. Owing to the large difference between the diameters of the inner and outer circular arrays of tubes, the liquids flowing past the inner arrays of tubes have much higher velocities than the heat--transfer liquid flowing past the outer arrays so that the heat transfer rates are highly different.
When it is desired to ensure an adequate heat transfer at the outer tubes, therefore, the liquid must be circulated at a high rate although this will result in an excessively high velocity of flow of the liquid near the inner arrays of tubes so that a high power is required to circulate the liquid and the heat transfer is not uniform too.
In the known multi-tube reactors having a circulating pump external of the reactor shell, the liquid is supplied to the reactor structure through an annular manifold, which is mounted on the outside surface of the reactor structure, and is connected through numerous ports to that space in the reactor structure in which the tubes are disposed. Liquid is returned to the circulating pump through another manifold which is mounted on the outside surface of the reactor structure.
The cross-section areas of the external manifolds must be selected for a flow of liquid at a rate which is one-half of the circulation rate. Also the lines connecting the manifolds to the circulating pump are often rather long. Short lines may be sufficient if two pumps rather than a single pump are used but this involves an undesired additional expenditure.